1. Field of the Invention
The present invention relates to a knee bolster, for an automotive vehicle, that absorbs the energy of impact that occurs between the instrument panel of the vehicle and the knees of an occupant during a collision. More specifically, the present invention relates to a knee bolster construction in which relative movement between the knee bolster and its associated energy absorbing structure is substantially eliminated.
2. Description of Related Technology
Knee bolsters are provided in the lower portions of an instrument panel, generally facing the legs of the passengers residing in the front seats of the automotive vehicle. During frontal impacts, one criteria for acceptable knee bolster performance is the effectiveness of the knee bolster in transferring impact loads to an energy absorbing structure located within the instrument panel. To accomplish this objective, the force exerted on the knee bolster, by the occupant's knees, is transferred to an energy absorbing structure that is configured to collapse during impact thereby dissipating the received energy. The energy absorbing structure collapses in a controlled manner so as to limit the depth that the knees of the occupant will intrude into the instrument panel. Controlling this collapse has proven to be difficult.
Current technology connects the knee bolster to the energy absorbing structure in several ways, depending on the materials used for the knee bolster. Generally, a knee bolster includes an outer skin coupled to an inner panel, which is conventional formed of either steel or plastic. When using steel, the inner panel is bolted, riveted or otherwise secured to the energy absorbing structures. While this is effective in securing the panel to the energy absorbing structure, it creates the possibility that the fasteners used in securing the inner panel will be visible as raised areas on the visible, class “A” surface of the skin.
When utilizing plastic, two sets of ribs have been provided to project from the interior surface of the inner panel and generally define a channel in a form outlining the shape of the energy absorbing structure. The energy absorbing structure is received between the two sets of ribs so as locate the inner panel relative to the energy absorbing structure. Relative movement between these two parts is not eliminated in that the parts are not fastened together. During an impact, the force of the impact may be sufficient to cause the energy absorbing structure to ride over the ribs and out of the channel or/and deform the ribs. If this happens, the inner panel will shift relative to the energy absorbing structure during impact, not allow the energy absorbing structure to properly absorb the impact. To overcome this and provide adequate stiffness, the size and number of ribs may become so great that their space requirement exceeds the available area on the surface of the inner panel.
Another approach is to use clips to attach the inner panel to the energy absorbing structure. While this concept adds a link between the two components, it may not be robust enough to withstand the impact load from an occupant of the vehicle during a collision.